Deformable, tacky tapes in general have been used to seal windows. However, such tapes can be problematic when used in sealing two window panes to form an insulated glass or "IG" unit. Such IG units must meet performance requirements which generally are far more demanding than single pane glazing.
In an IG unit, the space between the window panes is sealed, typically at room temperature and ambient pressure. Once installed, the temperature between the glass panes can increase dramatically during the summer and decrease dramatically during the winter. Since the air space is sealed, as the temperature changes, the pressure also changes--the air space will generally cause inward pressure to the window panes during winter and outward pressure during summer.
Such pressure changes can cause shifting of the window panes relative to one another, and the increased temperature during the summertime can soften the mastic. Over years of such temperature and pressure cycling, the mastic tape can exhibit unwanted flow.
As a result, rheological modifiers are generally added to tacky, deformable mastic tapes. However, rheological fillers can be hazardous. For example, many rheological modifying fibers and particles, particularly asbestos, can be harmful, if inhaled.
Carbon black is a rheological filler which is not particularly hazardous, relatively speaking, but can be messy and unpleasant to use. Furthermore, carbon black is manufactured generally by burning vaporized heavy oil fractions in a partial combustion reaction; such a manufacturing process is not particularly friendly to the environment, and consumers are increasingly interested in supporting environmentally friendly products.
Consequently, a need exists to provide an improved polymer matrix for window mastic strips, particularly for use in IG units, so that high loadings of rheological modifiers are no longer necessary.